Abstract Important components in estimating risks associated with exposure to nanomaterials include understanding the uptake, distribution, and elimination; the mode of acfion; and the pharmacodynamics of the effects of nanoparticles. Pregnancy and lactation are physiological states in which the distribution and effects of nanomaterials have not been extensively invesfigated. This project will invesfigate the absorption, distribution, metabolism, and excrefion of several nanoparticles with different size and charge properties. Investigations will be conducted with fullerene 060 and forms of multi-walled carbon nanotubes in female rats and mice, pregnant rats and mice, and in lactating rats and mice. The nanoparticles will be carbon-14 uniformly labeled by the RTI Synthesis and Characterization Core for conduct of these studies. Using three different routes of administration in female rats and mice (oropharyngeal aspiration, oral gavage, and intravenous [i.v.] injection) will provide information regarding the uptake and distribution processes for nanoparticles. Administration of the labeled nanoparticles to pregnant rats and mice by i.v, injection at different times in pregnancy will provide information about the ability of the nanoparticles to cross the placenta and result in fetal exposure. Analogously, i.v. administration to lactating rats and mice will enable evaluation ofthe secretion of nanoparticles into milk, resulting in exposure to offspring. The determinafion of the mass balance of radiolabel in urine, feces, blood tissues, and carcass at 5 time points over a period of 30 days following dosing will provide an enhanced understanding of the long-term fate of nanoparticles in the body. Quantitative whole body autoradiography will enable detailed characterization of the distribution of the nanoparticles. Examination of tissue samples with transmission electron microscopy will provide information on the subcellular localization of the nanomaterials. The effects of exposure to the carbon nanomaterials by oropharyngeal aspiration and i.v. administration will be investigated in the non-pregnant and pregnant (i.v. only) rodent by measuring arterial vascular reactivity, blood pressure, and cardiac ultrasound. The determination of markers of inflammation (cytokines), reproduction and development (hormones), and oxidative stress (8-hydroxydeoxyguanosine; 8- OHdG) will be conducted. The data obtained from Project 2 will be used in the development ofthe physiologically based pharmacokinetic and pharmacodynamic models constructed in Project 3.